Coke & Diet Coke: The Facts and the Fiction

Over the past week, you may well have seen a couple of graphics purporting to explain the effect that drinking a can of Coke or Diet Coke has on your body. They’ve been picked up by a range of online news and media sites, and as a result circulated widely. Unfortunately, although some of the information contained in them is correct, a lot of it is sensationalised, hyperbolic, or just plain wrong. This graphic is an attempt to sort the fact from the fiction, and give a clearer picture of what’s going on when you drink a can of Coke.

Before going any further, I should throw in a couple of disclaimers. Firstly, however incorrect the original graphics are, I suppose the intention behind them, getting people to drink fewer carbonated beverages, is by no means a bad one. There are certainly established health effects from drinking too many soda drinks, and by singling out these graphics for criticism, I’m not trying to diminish those effects in any way. My issue is merely with the accuracy of the information in these graphics that have been widely shared.

The creator himself has stated that “I don’t know exactly how accurate that infographic is… as I was not the original creator of the content,” which is a bad start. His intended message of enjoying soft drinks in moderation is laudable, but the use of incorrect information to disseminate this message devalues it. Including a handful of incorrect facts is likely to cause those that are correct to be disregarded by some readers.

As a final disclaimer, I’m not trying to discredit the original graphics out of any personal love of Coke. In fact, I don’t even particularly like the stuff (sorry, Coke lovers). However, I think that people need correct information to be able to make informed decisions about their Coke-drinking habits, so this is an attempt to provide that. I’ve tried to provide all references to the the claims made here within the text, to make them easy to verify, though I’ve also included links to the studies and sites cited at the foot of the page.

Does Coke contain 10 teaspoons of sugar?

The original Coke graphic actually begins with an entirely correct claim. A can of Coke does contain 33 grams of sugar, which is roughly 9-10 teaspoons. The graphic also states that this is ‘100% of your recommended daily allowance (RDA), which is a little wide of the mark, because there is no RDA for sugar. It probably intended to reference the World Health Organisation (WHO) guidelines on sugar, which state that added sugar should make up no more than 10% of your daily calorie intake. They also state that, ideally, further health benefits would be seen if this is reduced to 5% of your daily intake.

1 teaspoon of sugar contains 15 calories, so 10 would contain 150. In the UK, at least, the recommended daily calorie intake is around 2500 for men, and 2000 for women, so 150 calories would be 6% and 7.5% of these totals respectively. Clearly, this is a lot of sugar, and above the conditional limit of 5% set by the WHO – though still below the 10% mark. In summary, although the graphic gets RDA and the WHO guidelines confused, it’s not actually that far off the mark when stating that it’s a large percentage of the amount of sugar you should be ingesting per day.

Would you vomit from the sugar, if not for the phosphoric acid in Coke?

No. This point is plainly incorrect. It’s perfectly possible to drink a glass of water containing ten teaspoons of sugar without barfing everywhere, no phosphoric acid required. Is this amount of sugar good for you? Not really, no, but it’s not going to make you throw your Coke up onto the floor.

Does the phosphoric acid in Coke damage tooth enamel?

The infographic on Diet Coke states that ‘the phosphoric acid attacks the enamel in your teeth’. This is another mostly correct assertion. It’s perhaps not as instantaneous as the graphic suggests, but consuming a large amount of carbonated drinks could, over time, lead to tooth enamel damage due to their acidity. What the graphic doesn’t mention is that this is a phenomenon by no means limited to Coke. In fact, fruit juices are almost as problematic in this regard, as they can contain citric and/or malic acid, which can also damage tooth enamel over time.

The main thing the graphic ignores here is the issue of concentration; the concentration of phosphoric acid in coke is very low (around 0.055%). Compare this to the acid content of an orange, which is around 1%, and it becomes clear that concern about Coke’s acid content is being a little overblown. It’s also worth emphasising that we don’t hold food or drink in our mouths for a long period of time, so this lessens the deleterious effects of any acids on tooth enamel.

Does an insulin spike from high blood sugar cause your liver to generate fat?

Studies have actually shown that insulin spikes aren’t the main cause of fat production. The fat production from sweetened drinks is actually more associated with the metabolism of fructose in the liver. In fairness, though the graphic is incorrect in this regard, the accompanying text post does correctly discuss fructose, so it’s just a puzzle why the graphic was left with this incorrect claim. However, that sweetened drinks can lead to increased fat generation is not incorrect – and probably shouldn’t be a surprise!

Does caffeine work in the same way as heroin and cocaine?

The Coke graphic states that caffeine affects your brain in the exact same way as heroin, whilst the Diet Coke graphic compares the combination of caffeine and aspartame to that of cocaine. This claim, whilst having some roots in reality, is grossly sensationalised. Lots of things have an effect on the so-called ‘pleasure centres’ in the brain, and whilst dopamine is certainly involved in the addictive behaviours associated with heroin and cocaine, it’s also affected by perfectly mundane things like exercise and eating food.

Whilst the graphic claims that caffeine is directly involved in dopamine production, there’s no evidence for this. What it does do is prevent dopamine’s reabsorption. There’s actually no evidence that, at normal dietary levels, it affects the parts of the brain involved in addiction and reward, so comparing its action to that of heroin and cocaine is misleading.

Does caffeine have a diuretic effect in the body?

Another largely correct point – caffeine is a diuretic, although not a particularly strong one. Studies have found that, in doses equivalent to the amount of caffeine in 2 to 3 cups of coffee, caffeine can increase urine output. One thing that is worth noting though, is that the study in question notes that those who consume caffeinated beverages regularly build up a degree of tolerance to this effect.

Whilst Coke certainly isn’t as good at hydrating as plain water, it’s not as dehydrating as the graphic claims either, and doesn’t produce a net loss of fluids. The only drinks that do produce a net loss of fluid are those containing alcohol, and even that effect requires more than a couple of alcoholic drinks to be observed.

Is the combination of caffeine and aspartame a ‘potentially deadly’ one?

This is really a bit of a nothing statement, because anything, even water, can be deadly in high enough quantities. Are caffeine and aspartame deadly at the levels found in a can of coke? Nope. Not even remotely close. The text in the post accompanying the Diet Coke graphic uses the old ‘cocktail of chemicals’ trope, which I’ve always found is a classic sign that a tirade of bullshit is about to follow.

The post and graphic suggest that the combination of caffeine and aspartame can lead to the generation of excitotoxins. However, the research study cited to support this claim isn’t even talking about aspartame. Aspartame is a hugely maligned sweetener, of course, though I’ve already gone into the reasons why a lot of the negative claims surrounding it are incorrect. In short, some might not like the taste of aspartame, but really, you don’t need to worry about accidentally killing yourself by drinking a Diet Coke. Numerous reviews have shown it to be completely safe at normal dietary levels, and you’d have to drink over 30 cans of Diet Coke in a day to exceed the acceptable daily intake figure.

Does aspartame ‘trick’ the body into thinking it’s sugar?

Aspartame and other artificial sweeteners may taste sweet, but they don’t induce the same response in the body as sugar. Numerous studies have shown that aspartame does not affect insulin levels in the body after ingestion, so the claim in the Diet Coke graphic that it can ‘trigger’ insulin release is incorrect.

Coke isn’t great, but misinformation is worse

The most disappointing thing about these Coke graphics is the degree to which they’ve been shared by media sites, and the number of people who probably will have read them and believed every word. It really wouldn’t have taken a long time to look into some of the claims provided, and ascertain their accuracy, but that’s a process a lot of the media and news sites that have shared the graphics seem to have sidestepped. Sure, it might be difficult without a scientific background to recognise when information is erroneous, but it could have been as simple as asking for an expert opinion; for example, on chemistry subjects, the American Chemical Society even has a list of experts who can be contacted to obtain a response on science issues both in the media and elsewhere.

The large number of news and media sites merely reposted these graphics without a passing comment as to the information’s accuracy; in the majority of cases, all that was added was a click-bait headline. Buzzfeed, of all the places you might have expected, were actually one of the few sites who admirably dug a little deeper before reposting, and instead posted an excellent article refuting some of the claims in the original Coke graphic. Tech Insider also deserve a mention for their debunking of the subsequent Diet Coke graphic. Other news sites should take note.

As I stated back at the beginning, though the graphic sensationalises and gets some of the facts rather wrong, the take-home message that you should moderate your intake of carbonated drinks like Coke is a perfectly legitimate one. However, we should be trying to get that message across without resorting to sensationalising the facts, and making up extra ones to increase page views.

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References & Further Reading

• What’s wrong with that viral Coca-Cola infographic – C Kylstra & S Tamarkin, Buzzfeed
• Don’t believe that viral Diet Coke infographic – E Kincaid, Tech Insider
• Erosion of dentine & enamel in vitro by dietary acids – N X West & others
• The role of dopamine in effects of caffeine in animals and humans – B E Garrett & others
• Human hypothalamic response to sweet taste and calories – P A M Smeets & others
• Consumption of fructose and HCFS in men and women – K L Stanhope & others
• Actions of caffeine in the brain – B B Fredholm & others
• Aspartame: neurobehavioural evaluation of acute and chronic effects – P A Spiers & others
• Effect of aspartame on insulin in man – S E Møller
• Caffeine ingestion and fluid balance: a review – R J Maughan & others